Adjustable chair



FIG. 1 is a front view illustrating my new design;

FIG. 2 is a back view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a back view thereof; and,

FIG. 7 is a perspective view thereof. 

I claim the ornamental design for an adjustable chair, as shown and described. 